Apollo is a borough in Armstrong County, Pennsylvania, United States, 35 miles (40 km) northeast of Pittsburgh in a former coal-mining region. Apollo was settled in 1790, laid out in 1816, and incorporated as a borough in 1848. The town was originally known as 'Warren', but was later renamed to avoid confusion with another town in Pennsylvania of the same name.
The population in 1890 stood at 2,156; in 1900, 2,924; in 1910, 3006; in 1930, 3,406. The population was 1,765 at the 2000 census.
First settled in 1790, the log cabin home of the Drake family still stands from that era, and is one of the oldest buildings in Armstrong County. By the late 19th century the Apollo Iron & Steel Company dominated the local economy. In 1895, company's president, George Gibson McMurtry, hired famous landscape architect Frederick Law Olmsted to design a town for Apollo Iron & Steel's workers. The result was the neighboring town of Vandergrift. In 1911, Apollo became home to the first public library in Armstrong County.